Along with recent progress in electronic technology, materials having a low dielectric constant and a low dielectric dissipation factor are now in demand as materials of parts for use in computers and mobile communication equipment. To satisfy this demand, various materials are being developed. The materials include, for example, polybenzocyclobutene (R. A. Kirchhoff et al., Macromol. Symp. 54/55, 531 (1992)), fluorinated polybiphenylene ether (JP 10-74751 A), polyphenylene compound having a heterocyclic side chain (JP 9-278879 A), polyfumarate (JP 9-208697 A), polynorbornene (JP 5-214079 A), polyquinoxaline (JP 2705799 B), fluorinated polyquinoline (JP 6-500591 A), side chain allyl group-substituted polyphenylene ether (JP 64-69628 A, JP 4-183707 A, and JP 6-207096 A), and polyphenylene ether whose terminal is blocked with an allyl group or a propargyl group (JP 7-51625 B).
However, the above materials proposed in the prior art have various problems such as a low crosslinking density and a large linear expansion coefficient; low chemical resistance; poor tenacity; a large number of complicated steps required for the production of a resin from raw materials; and the need for a special solvent for shaping. Therefore, they have not been put to practical use yet.
The inventors of the present invention have proposed a vinylbenzyl ether compound which has low water absorption over a wide temperature range and a wide frequency range, a low dielectric constant and a low dielectric dissipation factor and satisfies the current strict requirements for electronic materials (JP 9-31006 A). This vinylbenzyl ether compound can be synthesized by reacting an aromatic compound having a hydroxyl group with a vinylbenzyl halide in a polar solvent in the presence of an alkali, or in a water/organic solvent mixed solution in the presence of a phase-transfer catalyst.
However, the requirements for dielectric properties of electronic materials are becoming more and more demanding. Next-generation communication devices have begun to appear, which require, in particular, a low dielectric dissipation factor, which cannot be satisfied even by the above vinylbenzyl ether compound.
It is therefore an object of the present invention to provide a polyvinyl benzyl compound which provides a cured product having high heat resistance, low water absorption, a low dielectric constant and a low dielectric dissipation factor, a process for producing the same, a curable resin composition comprising the same, and a cured resin obtained by curing said composition.
It is another object of the present invention to provide a substrate, prepreg and metal foil having a resin all of which have excellent dielectric properties over a high frequency range, in particular, a low dielectric dissipation factor, and high heat resistance.